It has become commonplace to use external fixators to repair various injuries and defects in bones. Such fixators are typically mounted on two or more transcutaneous pins embedded into the bone on opposite sides of the fracture or defect. An external frame is used to control the position and orientation of the pins relative to one another. The external frame typically will allow the positions of the pins to be adjusted in any of several degrees of freedom. By proper manipulation of the pins, it is possible to accurately and securely reduce the severed ends of the bone so that healing may be effected.
A major drawback with known fixators is the lack of freedom for placement of the pins. In particular, known fixators generally require the surgeon to choose the pin placement to accommodate the fixator being used. For many common types of fractures, this is not a problem because of the predictable presentations. For avulsion or other severe injuries to the hand and fingers, however, the ideal pin placement does not fit any predefined pattern. In addition, the pins should be installed through uninjured skin, further limiting acceptable pin placements. Thus, when treating such injuries, it is desirable to have a fixator that can accommodate a wide range of pin placement combinations as dictated by the nature of the injury rather than the mechanics of the fixator.
Because fixators remain in place on the patient's hand for considerable periods of time, it is important that the fixator be as compact and unobtrusive as possible. Moreover, the small size of the bones in the hand dictates that the fixator should allow the pairs of pins to be placed very close to one another. A fixator for use in the hand should also permit pins of various sizes to be used. Thus, small pins should be accommodated where there are small bones or bone fragments. Larger bones, on the other hand, may require larger pins to achieve adequate stability. One additional desirable property of a fixator for use on the hand is the ability to expand the fixator to hold additional pins at more than two locations. Lastly, a small bone fixator should work with either threaded pins or Kirshner wires, the latter being a standard inventory item in a variety of sizes at most hospitals.